add postgres 9.3 support for Ubuntu 14 and provide a way to tune encoding in createdb

Purpose is to install the available postgresql 9.3 version on current ubuntu and for those, who's system locale is UTF-8 to get the createdb call to succeed.

i am not sure if this
 - is the right way
 - is just hiding the symptom

On my test system, the postgres db was installed using example42-postgresql (via example42-puppetdb) and funnily has all templates in UTF8. So the createdb issued from puppetdb::postgresql does not work. It fails silently, because the creating code always exits 0 ("echo xxx" | psql). So my solution was to override template or encoding/locale via hiera (or site.pp). Since defined functions don't look up in hiera, i added a params class.
In this way it always take the value from params.
It should be something llike:
  undef => $postgresql::dbcreate::params::encoding, # (I would actually add the ncoding param in the main postegresql class)
  defaulf => $encoding,